First-Principles Studies of Contact Effects on Transport Properties of Metal-Molecule Junctions
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Date: 07-13-2006
Start Time:
11:00am
End Time: 12:00pm
Speaker: Jeffrey B. Neaton
From:
The Molecular Foundry, LBNL
Location: 414 Schapiro/CEPSR
Hosted by:
Center for Integrated Science
Abstract:
I will describe two separate theoretical studies of the role played by
metallic contacts in determining the low-bias transport properties of
metal-molecule junctions. Recent break-junction experiments have
reported the conductance of H2 molecular junctions drops by more than a
factor of two when Pt contacts were simply replaced with Pd. We are
able to explain these results surprisingly well by directly computing
the conductance of H2 with Pt and Pd metallic contacts using an ab
initio scattering state approach based on density functional theory.
Surface polarization of the metallic electrode affects the energetic
position of the frontier orbitals relative to the contact Fermi level.
We study a model metal-molecule contact, benzene physisorbed on
graphite. The benzene HOMO-LUMO gap, computed using the GW
approximation for the electron self-energy, is substantially altered
from its gas phase value, as well as differing from the results of DFT
calculations. A model calculation illustrates the impact of this
polarization for other conjugated molecules.
Biographical Sketch: Jeffrey B. Neaton received his Ph.D. in Physics
from Cornell University in 2000, under the guidance of Neil W.
Ashcroft. After a three-year stint as a departmental postdoc in the
Department of Physics and Astronomy at Rutgers University, he joined
the Molecular Foundry at Lawrence Berkeley National Laboratory in 2003,
first as a postdoc under Steven G. Louie and eventually as permanent
staff. He is presently acting lead scientist of the Foundry’s Theory
group. His current research interests center on computational
nanoscience, in particular the development and application of methods
for calculating the structural, spectroscopic, and transport properties
of inorganic and molecular nanostructures, particularly at interfaces.
Present areas of interest include the electronic properties of the
metal-organic interface, hybrid silicon-organic interfaces, and
single-molecule junctions; self-assembly; nanoparticle superlattices;
ultrathin epitaxial films of transition metal oxides, such as
ferroelectrics and multiferroics; and structural and electronic phases
of light elements under pressure.